Memory device for self-searching for boundary word line, method for operating memory device, and memory system including memory device

A memory system comprising:

• a controller configured to generate and output a search command when power is resumed after a sudden power-off (SPO), and perform a recovery operation in response to location information;
• and
• a first memory device including a plurality of memory cells which are coupled between a plurality of word lines and a plurality of bit lines, and a control circuit configured to:
• select a search group through a group-based binary search method for a plurality of groups obtained by grouping the plurality of word lines by a set number, in a state in which a search mode is entered in response to the search command,
• perform a checking operation of checking whether a boundary word line exists among word lines of the search group and at which location among the word lines of the search group the boundary word line is located, on the basis of a comparison between a magnitude of a search current obtained by summing currents respectively flowing through the plurality of bit lines and a magnitude of a reference current, by referring to a location table which stores locations of the boundary word line corresponding to values of a result of the comparison, in a state in which a detection voltage is applied to all word lines of the search group each time the search group is selected,
• generate location information indicating at which location among the word lines of the search group the boundary word line is located by checking a value of the result of the comparison in the location table, and
• output the location information to the controller.

A method for operating a memory device including a plurality of memory cells coupled between a plurality of word lines and a plurality of bit lines, the method comprising:

• entering a search mode in response to a search command;
• selecting a search group through a group-based binary search method for a plurality of groups obtained by grouping the plurality of word lines by a set number in an entry period of the search mode;
• performing a checking operation of checking whether a boundary word line exists among word lines of the search group selected in the selecting and at which location among the word lines of the search group the boundary word line is located, on the basis of a comparison between a magnitude of a search current obtained by summing currents respectively flowing through the plurality of bit lines and a magnitude of a reference current, by referring to a location table which stores locations of the boundary word line corresponding to values of a result of the comparison, in a state in which a detection voltage is applied to all word lines of the search group;
• and
• repeating the selecting and the checking when the boundary word line does not exist among the word lines of the search group in the checking operation, generating location information indicating at which location among the word lines of the search group the boundary word line is located by checking a value of the result of the comparison in the location table, and exiting the search mode after outputting the location information to the outside.